It is well known to provide a mechanism in which a combination of rack and pinion is used for converting a rectilinear motion of the rack into a rotary motion of the pinion. In such a mechanism, however, the pinion rotates in forward and reverse directions as the rack rectilinearly reciprocates. Thus, it has not been possible to obtain rotation in the same direction during both forward and reverse rectilinear movements of the rack.
For example, a conventional socket wrench includes an output shaft which is rotated in a certain direction by a ratchet mechanism. The socket wrench further includes a gear box in which the output shaft is housed and a lever projecting laterally from the gear box. After a socket for receiving a bolt or a nut is attached to the output shaft, the lever is manually turned. Only when the lever is turned in such a direction as to cause engagement of the ratchet mechanism, the output shaft is rotated by the turning force of the lever.
In such a socket wrench, the lever must be turned in a plane vertical to the output shaft of the lever. Therefore, if there is no space left for turning the lever, it is difficult to use the socket wrench. In some cases in which the space left for turning the lever is relatively small, the lever must be turned back before engagement of the ratchet mechanism advances a step. In such a case, the ratchet mechanism will not work, causing fastening or loosening operation of the bolt or the nut to be practically impossible.
Another example may include a rotary tool, such as a screwdriver and a nut fastener, which can be operated through rotation of a shaft having a grip at one end thereof. The grip is grasped by a hand of a user and turned to rotate a driver tip element formed at the extreme end of the shaft or supported by a chuck attached to the extreme end of the shaft.
In such a rotary tool, it is necessary to grasp and turn the grip by a hand. Thus, repetitive torsional action of the hand is required for turning the grip. This will reduce efficiency in operation, preventing fastening of many screws in a short period of time.